1. Field of the Inventions
The present inventions relate to Titanium-Tantalum base shape memory alloys, as well as actuators and engines using the said shape memory alloys, for example, Titanium-Tantalum base shape memory alloys with a reverse transformation temperature of over 50° C., as well as actuators and engines using such shape memory alloys.
2. Description of the Related Art
Ti—Ni base alloys are widely known shape memory alloys consisting of Titanium (Ti) and Nickel (Ni) which revert back to their original configuration upon application of heat up to their prescribed operating temperature, remembering their original shape.
However, in commercial Ti—Ni alloys, the peak transformation temperature (M*) is below 70° C. (343K), and the peak reverse transformation temperature (A*) is below 100° C. (373K). Thus, the operating temperature of the shape memory effect is less than approximately 100° C. Accordingly, conventional Ti—Ni base alloys are not suitable for operation as shape memory alloys at high temperature. For example, Ti—Ni—Cu base alloys are generally known to exhibit shape memory effect at temperatures in the range of 200K to 360K
The below mentioned alloys are generally well known high temperature shape memory alloys for use at high temperature (over 50° C. in the present application) with transformation start temperatures exceeding 110° C.
(1) (Ti—Zr)—Ni Alloys
In (Ti—Zr)—Ni base alloy, Titanium is substituted by 0-20 mol % (atomic percent) Zirconium, thus a corresponding martensite start temperature (Ms) from 373(K) to 550(K) is obtained.
(2) (Ti—Hf)—Ni Alloys
In (Ti—Hf)—Ni base alloy, Titanium is substituted by 0-20 mol % Hafnium (Hf), thus a corresponding martensite start temperature (Ms) in the range of 373(K) to 560(K) is obtained.
(3) Ti—(Ni—Pd) Alloys
In Ti—(Ni—Pd) base alloy, Nickel is substituted by 0-50 mol % Palladium (Pd), thus a corresponding martensite start temperature (Ms) in the range of 280(K) to 800(K) is obtained.
(4) Ti—(Ni—Au) Alloys
In Ti—(Ni—Pd) base alloy, Nickel is substituted by 0-50 mol % Gold (Au), thus a corresponding martensite start temperature (Ms) in the range of 300(K) to 850(K) is obtained.
(5) Ti—(Ni—Pt) Alloys
In Ti—(Ni—Pt) base alloy, Nickel is substituted by 0-50 mol % Platinum (Pt), thus a corresponding martensite start temperature (Ms) in the range of 280(K) to 1300(K) is obtained.
(6) Ti—Al Alloys
In Ti—Al base alloys, comprising 30-36 mol % Aluminum with the balance Nickel, a corresponding martensite start temperature (Ms) in the range of 273(K) to 1000(K) is obtained.
(7) Ti—Nb Alloys
In Ti—Nb alloys comprising 10-28 mol % Niobium with the balance Titanium, a corresponding martensite start temperature (Ms) in the range of 173(K) to 900(K) is obtained.
(8) Ti—Pd Alloys
As described in Kokai publication Tokukai No. Hei 11-36024, alloys comprising 48-50 mol % Palladium and 50-52 mol % Titanium by atomic percentage possesses a reverse transformation finish temperature (Af) in excess of 560° C. (833K).
(9) Ti—Ta Alloys
As described in Ikeda, et al. (Masahiko Ikeda, Shin-ya Komatsu and Yuichiro Nakamura, Effects of Sn and Zr Additions on Phase Constitution and Aging Behavior Ti-50 mass % Ta Alloys Quenched from β Singe Phase Region, Materials Transactions, The Japan Institute of Metals, page 1106-1112, issue 4, volume 45, 2004) alloys comprising 50% Tantalum by mass percentage (less than 30% converted to mol percentage) and the balance Titanium, or a mixture of Ti—Ta base alloys molten with 4% Tin (Sn) or 4% Zircon (Zr) by mass percentage possess a shape recovery start temperature in excess of 150° C. (423K).